1. Field of the Invention
The invention relates to an electrical machine with a horizontal axis, having a laminated stator core which is clamped in at least two vertical and mutually spaced annular support plates by means of mounting wedges distributed over its entire circumference, which support plates, in turn, are joined to the housing of the machine via mounting parts.
In this connection, the invention relates to a prior art which is found, for example, in European Patent Specification 0,166,114 or Swiss Patent Application 3557/88 of 23 Sept. 1988 of the applicant.
2. Discussion of Background
In gas-cooled electrical machines of the entire power range, large axial and radial strains occur in the laminated stator core which must be transferred to the housing, distributed as uniformly as possible.
In the air-cooled turbo generator known from European Patent Specification 0,166,114, this is carried out by laterally suspending the laminated stator core by means of support plates which are arranged in parallel, perpendicular to the axis of the electrical machine and are mutually spaced apart. To keep vibrations and thermal stresses occurring during the operating state of the electrical machine as small as possible, the support plates are constructed to be annular and are only connected in two areas of their horizontal plane of symmetry to the bottom part of the housing on both sides by means of mounting parts via extensions which extend vertically in a straight line. The by far greatest proportion of the circumference of the support plates is spaced away from the bottom and top part of the housing. The laminated stator core is clamped in the support plates by mounting wedges uniformly distributed over its entire circumference. The mounting parts consist of mounting plates which are in each case welded to the extensions of the support plates, and of tube sections with horizontal axis which are welded to the mounting plates. This type of mounting of the laminated stator core allows simple assembly, easy accessibility of the constructional parts to be welded together and ensures good quality of the welds.
However, the known arrangement mandatorily assumes a housing which is divided approximately in the horizontal plane of symmetry of the machine in order to be able to insert the laminated stator core. Thus, the transition to hydrogen cooling is not easily possible because, in particular, the interfaces between the bottom and top part of the housing are problematic with respect to sealing.
To be able to use an undivided housing in such machines, it is proposed in the Swiss patent application initially mentioned to have different diameters for the mounting plates attached to the annular support plates, which dimensions, seen from one machine end, are stepped towards the other end and, correspondingly, similarly to step the associated mounting points at the housing. In this arrangement, the transverse walls are constructed of two parts and consist of a first ring which is attached to the laminated stator core, and a second ring which is attached to the housing, in which arrangement the free ring ends overlap and a seal is provided at the overlap which is elastic at least in the axial direction. Seen from the other machine end, the outside diameters of the first rings are in each case smaller than the inside diameter of the second ring adjacent to it.
Such a machine allows a housing which is undivided (in the axial direction) because the laminated stator core (provided with the stator winding, if necessary) can be inserted into the housing. Closed housings of this type can be made gas tight in a much simpler manner and also withstand the higher gas pressures (approximately 10 bar) in the case of hydrogen cooling.
Both in the solution according to European Patent Specification 0,166,114 and in the solution according to the Patent Application initially mentioned, laminated-core vibrations, which are transferred via the housing and the housing support to the machine foundation, occur as a consequence of the rotating magnetic field of the rotor.
To eliminate these disturbing influences of the laminated-core vibrations, caused by the rotating magnetic field of the rotor, of alternating-current generators on the machine foundation, it is known that designs have been developed in which either the housing is elastically supported with respect to the foundation or the laminated core, which is held in an intermediate frame, is elastically connected with interposition of springs to the housing which is rigidly mounted on the foundation. Whilst the first-mentioned arrangement has the disadvantage that the vibrations occur at the housing and, under certain circumstances, cause more or less disturbing noises, the arrangement mentioned secondly, which also enables vibrations to be kept away from the housing, results in a relatively complex stator construction if the springs--which enable the radial excursion of the laminated core--are arranged tangentially with respect to the laminated core and are connected to the latter and to the outer housing frame.
It is also already known to mount within the stator housing spring members which are axially arranged at the ribs of the latter at which the laminated core is supported in such a manner that it can oscillate radially, utilizing the spring arrangement. In this arrangement, it is found that vibration loads are transferred to the machine housing over the entire length of the laminated core.